1. Field of the Invention
The present invention relates to structures for the containment of waste and more particularly to barriers used in such structures. It also relates to the drainage of, and the reduction of frost heave in, pavement and other geotechnical structures.
2. Brief Description of the Prior Art
As increasing amounts of municipal and other wastes are disposed of in landfills, a need has become apparent to reduce or eliminate the infiltration of water into such landfills. One approach to reducing the infiltration of water is disclosed in U.S. Pat. No. 5,550,315 to Stormont, the contents of which are incorporated herein by reference. This patent discloses a system in which waste sites are capped or covered upon closure. The cover structure incorporates a number of different layers each having a contributory function. One such layer is the barrier layer. Traditionally, the barriers have been compacted soil and geosynthetics. These types of barriers have not been successfully implemented in unsaturated ground conditions like those found in dry climates.
A Capillary barriers have been proposed as barrier layers in dry environments, but the diversion length of these barriers has been found to be inadequate. An alternative to the capillary barrier is an anisotropic capillary barrier. An anisotropic capillary barrier has an increased diversion length, which results in more water being diverted laterally, thereby preventing the majority of water from percolating in a downward direction through the barrier. Number of drawbacks, however, may attend the use of the Stormont system. That is, the barrier used in the Stormont system limits water flow downwardly, but there is no means for the lateral drainage of water moving upward. The Stormont system is used to dirvert infiltrating water, but not as a drain for unsaturated soils noras an integral part means of reducing pore water pressure in the overlying or underlying soils nor the purpose of reducing frost heave in the overlying soil.
A need, therefore, exists for a geotechnical structure with a moisture barrier that limits water flow not only downwardly, but also upwardly, and to provide lateral drainage of unsaturated soils overlying and underlying the barrier.